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4.4.5 Average thickness of overburden <br />The average thickness of overburden is estimated to be three feet, based on soil borings taken <br />across the extent of the Site. <br />4.4.6 Detailed Map of Haul Routes <br />Figure 5: Haul Routes, illustrates the extent of the haul routes within the City limits. Local roads <br />will be used for approximately % mile to access US 169. County and state highways will be used <br />for the majority of hauling. Local roads, beyond Baldwin to 225th Avenue NW, will be used only <br />as needed for local deliveries. <br />4.5 Plan of Operation: <br />Active mining will begin by stripping topsoil and overburden from a portion of the Site. Overburden <br />and topsoil will be shaped into perimeter berms. To reduce exposed soils and the potential, dust, <br />sedimentation and erosion, stripping and construction of berms will occur in phases as mining <br />progresses through the Site. Berms will be constructed to maintain existing drainage patterns. <br />Extraction of the aggregate deposit will be accomplished with loaders, dozers, excavators and off - <br />road trucks. <br />Mining will extend into the water table. Sand and gravel will be mined below the water table using <br />wet mining methods; a backhoe, drag line or dredge. The depth of excavation below the water table <br />will range between 50 feet and 100 feet depending upon the quality of aggregates encountered and <br />equipment utilized. Mining below the water table may occur over any portion of the floor of the <br />mine. Portions of the excavation below the water table may be backfilled, but the majority will <br />remain as created waterbodies at the conclusion of mining and reclamation. A maximum of <br />approximately 30 -35% of the property may contain created waterbodies upon final reclamation. <br />Final slopes around the perimeter of the Site, not adjacent to created waterbodies, may be finished <br />at a maximum slopes of 3:1 (H:V). Final slopes adjacent to waterbodies that will remain as part of <br />final reclamation will be constructed at a maximum slope of 4:1 (H:V). The 4:1 (H:V) slope will <br />extend to at least six feet below the normal water elevation around the perimeter of waterbodies. <br />Processing equipment: crushing, screening, and washing, will be located on the floor of the mine to <br />provide screening and reduce dust and sound emissions from the Site. The primary crusher will <br />typically be located adjacent to the active face where materials will be crushed and then conveyed <br />or hauled to the main processing area for additional crushing, screening and or washing. Material <br />stockpiles will be established around the processing plants. <br />The washplant will operate seasonally during nonfreezing weather conditions (generally April — <br />November). The washplant will discharge process water into a series of on -site ponds that will be <br />established on the floor of the mine. These ponds will allow fine sediments that are in the <br />washwater discharge to settle. Clarified washwater will be returned to the washplant for reuse. <br />Washwater will not be discharged from the site. Portable toilets will be used at the Site to serve <br />employees. <br />Tiller Corporation Sunde Engineering, PLLC <br />Conditional Use Permit Application Page 15 <br />City of Elk River <br />